Nitrate reduction

Options

A. is performed by plants.
B. takes place in mitochondria.
C. is catalyzed by the enzyme nitrogenase.
D. includes the reduction of nitrite ions to nitrate ions.

Answer

### Step-by-Step Solution for Nitrate Reduction

1. **Understanding Nitrate Reduction**: Nitrate reduction refers to the biochemical process where nitrate ions (NO3-) are converted into nitrite ions (NO2-) and subsequently into ammonium ions (NH4+). This process is crucial for plants as it allows them to utilize nitrogen from the soil.

2. **Process Overview**: The reduction of nitrate involves two main steps:
- Conversion of nitrate (NO3-) to nitrite (NO2-).
- Conversion of nitrite (NO2-) to ammonium (NH4+).

3. **Enzymes Involved**:
- The enzyme **nitrate reductase** catalyzes the first step, converting nitrate to nitrite.
- The enzyme **nitrite reductase** catalyzes the second step, converting nitrite to ammonium.

4. **Location of Nitrate Reduction**: This process primarily occurs in the **roots** of the plant, where the nitrate is absorbed from the soil. It does not take place in the mitochondria, as the question suggests.

5. **Clarifying Misconceptions**:
- The statement that nitrate reduction occurs in mitochondria is incorrect; it occurs in the cytoplasm of root cells.
- The enzyme nitrogenase is not involved in nitrate reduction; it is primarily responsible for nitrogen fixation, which is a different process.

6. **Conclusion**: Based on the analysis, the only correct statement regarding nitrate reduction is that it is performed by plants. The other statements regarding the location and enzymes involved are incorrect.